Various needs and trends are currently emerging, including,
the need to make the operation of card reading apparatus more secure. To achieve this, it is necessary:
1) to assure that the card is inserted correctly before the microcircuit is powered up and the dialog sequence with the latter is begun.
2) to assure rapid disconnection of the power supply from the card in the event of a misoperation "pulling out" of the card, to limit the risk of damage to the circuits and/or fraud attempts.
To this end, current reading systems include a device for detecting correct insertion of the card which uses an end-of-travel contact whose closure conditions, the start of electronic initialization read-write sequences controlled by the electronics of the reader and monitored by a microprocessor to conform to a particular chronology for which the reader:
powers up the microcircuit, PA1 activates the data input-output channels, PA1 activates the microcircuit clock channel, and PA1 performs a microcircuit initialization sequence. PA1 insertion of the card is assumed to be correct on activation of the end of travel contact; PA1 the initialization sequence begins by the application of voltage to the card power supply brushes; PA1 before powering up and during the initialization phase of the card the initialization (reset channel) brush is at logic 0 potential; PA1 during the initialization sequence the signal brushes are in a so-called "high impedance" state. PA1 setting the initialization channel of the microcircuit of the card to 0, PA1 setting the signal channels of the card to the high impedance state, PA1 cutting off the power supply from the card.
The microcircuit must then respond to the initialization sequence in a particular way in order to enable dialog between the microcircuit of the card and the microprocessor of the reader. At the end of this dialog the microprocessor performs a card deactivation sequence.
Microcontroller-based dedicated circuits are available which manage these sequences of initializing and ending dialog with the microcircuit and which additionally monitor overvoltages and short-circuits on the card.
Nevertheless, if the card is pulled out, the powering down and deactivation of the various channels entails:
1) opening of the card presence contact,
2) detection by microprocessor or the dedicated microcontroller of this opening before powering down of the card can be initialized by a sequence of logical operations.
The card can be pulled out at speeds up to 1 m per second. This requires a card presence contact having a travel of less than 0.1 mm to guarantee a reaction time less than 100 .mu.s compatible with execution of the card emergency deactivation sequence.
A first problem is that there is often a lack of precision as to the position of the end of travel contacts, especially if these are horizontal or mounted on a frame independent of the reading frame.
A second problem is that the reaction time of the microprocessor or the microcontroller depends on its internal program and on the clock frequency sequencing it.
The applicant has found that: